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<title>Booleans</title>
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</div><hr /><div id="language.types.boolean" class="sect1">
<h2 class="title">Booleans</h2>
<p class="simpara">
This is the simplest type. A <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> expresses a truth value. It
can be either <strong><code>TRUE</code></strong> or <strong><code>FALSE</code></strong>.
</p>
<div class="sect2" id="language.types.boolean.syntax">
<h3 class="title">Syntax</h3>
<p class="para">
To specify a <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> literal, use the keywords <strong><code>TRUE</code></strong> or
<strong><code>FALSE</code></strong>. Both are case-insensitive.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$foo </span><span style="color: #007700">= </span><span style="color: #0000BB">True</span><span style="color: #007700">; </span><span style="color: #FF8000">// assign the value TRUE to $foo<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
Typically, the result of an <a href="language.operators.html" class="link">operator</a>
which returns a <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> value is passed on to a
<a href="language.control-structures.html" class="link">control structure</a>.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// == is an operator which tests<br />// equality and returns a boolean<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">$action </span><span style="color: #007700">== </span><span style="color: #DD0000">"show_version"</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"The version is 1.23"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// this is not necessary...<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">$show_separators </span><span style="color: #007700">== </span><span style="color: #0000BB">TRUE</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"<hr>\n"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// ...because this can be used with exactly the same meaning:<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">$show_separators</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"<hr>\n"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</div>
<div class="sect2" id="language.types.boolean.casting">
<h3 class="title">Converting to boolean</h3>
<p class="simpara">
To explicitly convert a value to <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>, use the
<em>(bool)</em> or <em>(boolean)</em> casts. However, in
most cases the cast is unnecessary, since a value will be automatically
converted if an operator, function or control structure requires a
<span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> argument.
</p>
<p class="simpara">
See also <a href="language.types.type-juggling.html" class="link">Type Juggling</a>.
</p>
<p class="para">
When converting to <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>, the following values are considered
<strong><code>FALSE</code></strong>:
</p>
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
the <a href="language.types.boolean.html" class="link">boolean</a> <strong><code>FALSE</code></strong> itself
</span>
</li>
<li class="listitem">
<span class="simpara">
the <a href="language.types.integer.html" class="link">integer</a> 0 (zero)
</span>
</li>
<li class="listitem">
<span class="simpara">
the <a href="language.types.float.html" class="link">float</a> 0.0 (zero)
</span>
</li>
<li class="listitem">
<span class="simpara">
the empty <a href="language.types.string.html" class="link">string</a>, and the
<a href="language.types.string.html" class="link">string</a> "0"
</span>
</li>
<li class="listitem">
<span class="simpara">
an <a href="language.types.array.html" class="link">array</a> with zero elements
</span>
</li>
<li class="listitem">
<span class="simpara">
an <a href="language.types.object.html" class="link">object</a> with zero member
variables (PHP 4 only)
</span>
</li>
<li class="listitem">
<span class="simpara">
the special type <a href="language.types.null.html" class="link">NULL</a> (including
unset variables)
</span>
</li>
<li class="listitem">
<span class="simpara">
<a href="ref.simplexml.html" class="link">SimpleXML</a> objects created from empty
tags
</span>
</li>
</ul>
<p class="para">
Every other value is considered <strong><code>TRUE</code></strong> (including any
<a href="language.types.resource.html" class="link">resource</a>).
</p>
<div class="warning"><strong class="warning">Warning</strong>
<p class="simpara">
<em>-1</em> is considered <strong><code>TRUE</code></strong>, like any other non-zero
(whether negative or positive) number!
</p>
</div>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />var_dump</span><span style="color: #007700">((bool) </span><span style="color: #DD0000">""</span><span style="color: #007700">); </span><span style="color: #FF8000">// bool(false)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) </span><span style="color: #0000BB">1</span><span style="color: #007700">); </span><span style="color: #FF8000">// bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) -</span><span style="color: #0000BB">2</span><span style="color: #007700">); </span><span style="color: #FF8000">// bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) </span><span style="color: #DD0000">"foo"</span><span style="color: #007700">); </span><span style="color: #FF8000">// bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) </span><span style="color: #0000BB">2.3e5</span><span style="color: #007700">); </span><span style="color: #FF8000">// bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) array(</span><span style="color: #0000BB">12</span><span style="color: #007700">)); </span><span style="color: #FF8000">// bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) array()); </span><span style="color: #FF8000">// bool(false)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool) </span><span style="color: #DD0000">"false"</span><span style="color: #007700">); </span><span style="color: #FF8000">// bool(true)<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
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